These transport pipes can be SCR type (Steel Catenary Riser) pipes, i.e. metal pipes assembled by welding and running through the water depth. FIG. 1 hereafter describes the architecture of this type of pipes. Reference number 1 refers to a floating support, a tanker for example, connected to the subsea wellheads (not shown) by a riser pipe 2 whose upper end is suspended from the ship and a portion 3 of which lies on the sea bottom 4. This type of J-shaped metal pipe has a critical point 5 in the touchdown point zone TDP.
As regards the structure, the weak point of a SCR type production pipe is located at the level of the parting zone close to the first touchdown point.
In the lower zone of the riser, near to the TDP, the curvature exhibits a maximum that is translated at the mechanical level into a bending stress peak. When the riser is subjected to a dynamic stress, as it is the case in the presence of wave motion, the greatest curvature variations (and therefore the stress variations) are observed in the TDP zone, locally inducing a significant fatigue increase.
The object of the present invention is to limit the stresses and therefore the fatigue in this critical zone.